The death toll from a car bombing in the southern Philippines rose to eight Tuesday, as authorities investigate whether a local official was the intended target.

Police said two people, including a police officer, died overnight following the Monday blast on the island of Mindanao. At least 30 others were wounded in the attack.

The bomb went off on a major street in Cotabato City as a car carrying city administrator Cynthia Guiani-Sayadi was passing by. She escaped unhurt, but one her of bodyguards in a nearby security van was killed.

Authorities say Guiani-Sayadi had received threats in recent days, but they have not named any possible suspects or groups who may have been responsible.

There was no immediate claim of responsibility for the attack. A previous bombing struck the city of Cagayan de Oro on July 26, killing eight people at a restaurant.

A breakaway Islamist rebel faction has vowed to continue fighting for a separate homeland for minority Muslims in the southern Philippines. The Bangsamoro Islamist Freedom Movement split from the main Moro Islamic Liberation Front, which is engaged in peace talks with the Philippine government.

Mindanao also is plagued by armed gangs involved in kidnapping and extortion.

The United States issued an alert last month, warning Americans to avoid travel to southern Philippine regions such as Mindanao. It cited a "high threat of kidnapping of international travelers and violence linked to insurgency and terrorism."